The Science of Dimetrodons

Dimetrodons lived about 35 million years before the first dinosaurs did. They looked a lot like dinosaurs with their scales and lizard-like bodies, but they actually weren't even reptiles. The difference is in their skulls. Dinosaurs had two holes behind their eye sockets where some of the lower jaw muscles attached to their skulls. Dimetrodons only had one of these holes. This difference helped scientists figure out that Dimetrodon were part of the same group of animals as us humans.